This invention relates to a mastering machine for an optical disk, and more particularly to a mastering machine suitably used to make a master disk for on-land recording having concentric or spiral guide grooves and recording data between these grooves.
For an on-land recording master disc, it is necessary to record not only data but also header signals, such as track addresses and sector addresses between the guide grooves.
The mastering machine used for this purpose are proposed in Japanese Patent Laid-open No. 50733/1985 and Japanese Patent Laid-open No. 13458/1986 (U.S. application Ser. No. 685,123 and its continuing application). In these apparatuses, the light emitted from a laser light source is divided into a guide groove recording beam and a header recording beam by a beam splitter, and these beams are modulated in intensity according to the signals by light modulators. The modulated beams are then synthesized by another beam splitter and irradiate a photosensitive layer, which is formed on a disk, through a recording lens, and thus signals are recorded on the photosensitive layer. In order to record a header signal between the guide grooves, the guide groove recording beam is set so that it enters a lens at a corresponding incident angle, which is set by mirrors, with respect to the header recording beam.
In these conventional apparatuses, the incident angles of the guide groove recording beam and header recording beam are determined in accordance with the accuracy of the mechanical position of each of the elements constituting an optical system. Consequently, when the position of each of these elements varies due to the variations of the temperature and mechanical vibrations, the distance between the patterns, which are recorded on the photosensitive layer, of the header and guide grooves varies.
If the recording and reproduction of data are done on an optical disk made from the master disk, which is obtained by developing the photosensitive layer, variations in the level of read signals and crosstalks from an adjacent track signals would occur, and this causes the misreading of the data.